A 2.5 Gb/s dual-wavelength packets parallel buffering in dual-loop optical buffer (DLOB) adopting semiconductor optical amplifier (SOA) as the nonlinear element was demonstrated. Because of the random fluctuation of the combined power by different wavelength signals, the phase difference originating from the cross phase modulation of SOA fluctuates randomly too. Taking the absorption loss into account, we modify the gain characteristic curve of SOA and fit it with experimental values. The characteristic curve is described exactly. We also theoretically analyze the dual-wavelength buffering and propose to set the power of control signal to minimize the fluctuation of the phase difference.